Alles over licht en lampen

Volledig spectrum daglicht

Vitamine D3, hoe ontstaat dit uit zonlicht in de huis van mens en dier?

 http://arc.org.za/Vitamin_D.htm



http://www.anapsid.org/uvd3.html

http://www.anapsid.org/iguana/bernard-d3.html


http://www.sciencenews.org/articles/20041009/bob8.asp

 

Wat ziet een reptiel?

 

      Relatieve vochtigheid

Ik geef hieronder een ongecompliceerd voorbeeld, maar de getallen die er in staan die kloppen dus niet. Ik heb nu even geen tijd om dat precies op te zoeken, dus bedenk maar dat ze er alleen genoemd worden om het principe duidelijk te maken. In lucht van 20 graden Celcius zit een bepaalde hoeveelheid water. Laten we zeggen 6 gram per liter, maar bij die temperatuur zou er méér water in kunnen zitten. Het maximale is 10 gram. Daarom noemen we dit een Relatieve vochtigheid (RV) van 60%. 6 gram is namelijk 60% van 10 gram. Bij een hogere temperatuur kan er meer water in de lucht. Als dus de temperatuur stijgt naar 30 graden, dan blijft de hoeveelheid water van 6 gram per liter lucht gelijk, maar ten opzichte van het maximale wat er in kan, is dit maar 40%. Je hebt dus de gelijke hoeveelheid water, maar er zou veel méér in kunnen. Als de temperatuur omlaag gaat, dan kan er minder water in de koudere lucht. Bij 15 graden kan er maar 5 gram water in de lucht. Als er eerst 6 gram was, dan zit de lucht bij die tien gaden helemaal vol, dat het dus 100% Relatieve Vochtigheid. Dat ene grammetje water wat je nog over had, kan maar een ding doen en dat is condenseren tegen het koudste oppervlak, en dat zijn meestal de ruiten. Je ziet dus dat zelfs als je niet sproeit in je terrarium, je dus op een dag drie keer een andere RV hebt doordat de temperatuur in je terrarium wisselt. Als je denkt dat de vochtigheid in je terrarium te hoog of te laag is, dan dien je eerst te kijken of de temperatuur nog gelijk is. Vaak wordt er gesteld dat een bepaald reptiel een RV nodig heeft van bijvoorbeeld 80%. Maar daarbij moet je dan wel de temperatuur er bij weten! Iedereen kan een RV in het terrarium hebben van 80%, als je de temperatuur maar laag genoeg maakt. Maar dat is dus niet de bedoeling. Zorg eerst voor een goede temperatuur voor je dier en kijk dan pas of je RV klopt. Is die te hoog, dan moet je meer ventileren, is de RV te laag, dan moet je sproeien. Wat je ook vaak hoort is dat je 's avonds moet sproeien omdat dan de RV omhoog moet. In de natuur zou dit ook zo zijn. Wat er in de natuur gebeurt, is dat de temperatuur 's avonds omlaag gaat, er kan minder vocht in de afkoelende lucht en dat vocht slaat dan neer als dauw op het gras. Ditzelfde zou je dus moeten zien na te bootsen in je terrarium. Op de dag een juiste temperatuur en RV voor je dieren. Tegen de avond verminder je de warmte (lamp uit) en je zult zien dat wanneer je op de nachttemperatuur voor je dieren uitkomt, dat dan de RV ook stijgt tot het percentage dat voorkomt in de natuurlijke omgeving van je dier. Als je dit enkele dagen blijft volgen, dan zul je zien dat je op het heetst van de dag zult moeten sproeien om de RV te kunnen halen en niet 's avonds. Frans, droge vingers van het typen.

 

 

Voeding Landschildpadden http://www.sulcstatn.addr.com/index.html http://www.anapsid.org/tortdiet.html Diet Considerations of Captive Tortoises http://www.anapsid.org/dietcons.html

Re: Are our 6.2 Solarmeters still useful? (was: Exoterra 10)   Hi, everyone. Certainly Veronica's questions are excellent ones. Light measurement is SO complicated! I guess it's no wonder that we all find it so hard to get our heads round. It's taken me three years of doing very little else in my spare time, to get as far as I have (which isn't very far) in understanding what our little meters "see" and what that means. Steve's comments here are spot on. I used the analogy of "strong" and "weak" alcoholic drinks, a while back, to illustrate what Steve calls "sharp" and "dull" UVB. As he says, our 6.2 meters measure the total amount of UVB but don't measure how "concentrated" it is, how much "zap" it has in it, if you like. So if your meter reads 100uW/cm2 and you're pointing it at a ZooMed Reptisun 5.0 TUBE, at that distance you have 100 microwatts of gentle zap... about UV Index 2.3. That's similar to the gentle zap of daylight through clouds at mid-day in the summer, UV Index 2.0. If your meter reads 100uW/cm2 and you're pointing it at a ZooMed Reptisun 10.0 COMPACT, at that distance you have 100 microwatts of really over-the-top powerful zap... about UV Index 9.2. This is similar to sub-tropical hot sunshine and I don't know if any reptiles actually ever bask at those sort of UV Index levels. These type of lamps have un-natural very low wavelengths not found in sunlight (which is where the zap comes from) and this may even be harmful in itself. So the 6.2 meter is accurate (in that there really is 100uW/cm2) but not necessarily helpful in deciding what distance to use a lamp at... because you can't just say, "I think 100 - 200uW/cm2 at the basking spot is good for iguanas", or whatever, like we used to. That is still true, of course, for natural sunlight and for lamps that are similar in "zap" to natural sunlight. But it is NOT true for these "high-zap" lamps. What we need to do, is to design and publish some simple Conversion Charts which people with Solarmeter 6.2s can use. You need a separate Conversion Chart for each brand and type of lamp. So people can say: "I have an ExoTerra ReptiGlo 10.0 Tube. I want to fix it up so I get UV Index 3 at my basking spot. What readings should I aim for, on my Solarmeter 6.2?" I am working on this right now, which is where I got the figures below for, for the different lamps. My project for this winter is to get all of this stuff online. The Conversion Charts are easy to make, and they work in Excel. All you need, to make one for each lamp brand, is a sample lamp, plus a 6.2 and a 6.5 meter. The million-dollar question though, is highlighted by Steve's comment - How much short-wave UVB is TOO much? I'll rephrase that to: How much UV Index do we want at a basking spot? AHA. The million dollar question. There's only one way to find out.... by going out there into the wild habitat and watching reptiles...and finding out what UV Index it is, where they are basking. Other ways to find out, are too complicated... we can't measure the vitamin D3 production in the skin of hundreds of different species of reptile (all different)under different UV lights, we can't even measure the normal D3 levels in the blood of those hundreds of species in the wild. We can't do more than guess at the UV Index they will choose, from the sun recordings made worldwide by meteorological stations, because these give the UV Index of full sunshine measured all day. Even sun- loving reptiles only bask in full sunshine at certain times of the day. Some reptiles never bask at all, but pick up all their UV from the plentiful daylight UV still found in the shade. We don't yet know what the UV Index of this is.... we are only beginning to have recordings of what the Total UVB of this is, in fact. If we are going to base our practical measurements on UV Index, rather than on Total UVB, we will need to measure both of these in the wild, too. Don't give up hope though. We only need ball park figures!! As long as we get it approximately right, and don't give our reptiles dangerously high levels or pathetically low ones, they know what they need. They will find the distance from the lamp that's about right, and sit under it for as long as they need to (as long as their other requirements, eg. heat and visible light, are being met). > Frances seems to consider UVI above a typical tropical mid-morning >level as approaching excessive Well... why I say that is only because when I was in Australia, I tried to get UV readings from places where I saw basking lizards, at every opportunity. And we never saw any, basking in the sun in the middle of the day. The highest UV Index where a lizard was, measured 7.6, and it was at 10am on a bright sunny day in Kakadu, in tropical Northern Territories. Scientists among you will no doubt think it's hilarious -and ridiculous- that I'm using that ONE sighting to suggest a possible safe maximum. Yes, I totally agree, it's pathetic. But it's the only information I have, to date. I don't know of anyone else who's measured this yet - no doubt as people start to do so, we'll revise everything in light of their figures. Also, in the recent cases of eye and skin problems with "problem" lamps, all the cases occurred when the UV to which they were exposed was higher than UV Index 8 - 9. I'll try to make up a chart of all the UV Index and Total UVB recordings I have, for reptile sightings, and put it in the files here. If anyone else has taken wild reptile sightings with UV recordings please post them! (Either Solarmeter 6.2, 6.4 or 6.5....) There is a study being undertaken right now, as far as I know, in the Cayman Islands with the endangered Blue Iguanas, measuring UVB and UVI at lizard locations throughout their day. Really exciting stuff! All the best Frances   Hi, Tracie I'm afraid all these technical terms are getting you in a bit of a mix-up. Lux, microwatts per square cm (uW/cm2), lumens (lm), nanometers (nm) and Kelvin (K) are all totally different things, you can't convert them at all. It's like asking, how many apples are in a rainbow. I don't know of any good books on light measurement I'm afraid, and when I started reading about it, I too found it very baffling. All I can say is - don't give up! It slowly sinks in, it really does. Wikipedia is useful, to look up words like lux, light, ultraviolet and photometry... but sometimes the articles are quite detailed and challenging. But worth a look. There are two ways of measuring light. Wikipedia has helped me out here; it says: "Photometry" is the science of measurement of light, in terms of its perceived brightness to the human eye. It is distinct from "radiometry", which is the science of measurement of light in terms of absolute power. When we use the Solarmeter 6.2, we get "radiometry". The measurements are in Watts, or micro-watts, per square centimetre... they are power measurements. So you get a reading of, for example, 1 µW/cm² . You do NOT need to understand all this to use a Solarmeter, and to use it very accurately. All you need is a steady hand, a tape measure, and a pencil to write down the readings. Honest. Wavelengths of light are measured in nanometers (nm). This is not a measurement of power or brightness at all... I guess the easiest way to think of it, is that the wavelength is the code number for a precise colour in the rainbow - a rainbow that includes colours invisible to us (eg. ultraviolet). So if I said "light of 520nm" I am talking about light of a very specific colour of green. If I say "wavelengths between 400nm and 475nm" I am talking about all colours of purple and blue as a group, from deepest purple to greeny- blue. A broadband UVB meter measures all UVB light between wavelengths 280nm and 320nm. It sees how much "power" it's getting from the lamp from ALL those wavelengths, and gives you a total reading, in µW/cm². A spectrometer can look at much smaller numbers of wavelengths, eg. just one or two, and do the same thing. It will tell you, in µW/cm², how much "power" it can see at the wavelengths you ask it to look at. But people like to know other things about a lamp. Our eyes are not "radiometers" - they see different amounts of "brightness" not Watts or micro-watts. So when we measure the "brightness" of a lamp we use "photometry" and the commonest "photometer" is a lux meter. It looks and works just like a Solarmeter but the readout is adjusted to make allowances for how human eyes see "brightness"... the readout is in lux, and refers to all the visible light. One lux is one lumen per square metre. (We could write this as 1 lx, or 1 lm/m²) We also like to know what color light a lamp has. Is it an orangey or a bluish light? We could look at the power coming out at each wavelength and calculate it like that.... but you need a spectrometer and a computer to do "color analysis". An easier way is to compare the redness or blueness with the glow from heating something. If you heat a metal bar, for example, it glows red, then as it gets hotter and hotter, it goes yellow then white then blue-white. The Color Temperature of a lamp in Kelvin (K) (which is a temperature measurement like °C) tells you how it compares with the color of a reference item called a 'black body radiator' heated to that temperature. Cooler color temperatures (eg, 3,000K) mean an orange glow whereas higher colour temperatures (eg. 12,000K) are bluish. Nice white daylight is about 5,500K to 6,500K. I don't know whether I've now confused you more... or been of help! -Frances